The present invention relates to a supporting mechanism of a magnetic head slider and a magnetic disk device equipped with the same, and more particularly relates to a supporting mechanism of a slider mounted with a magnetic head which performs contact reading/writing of a magnetic disk and a magnetic disk device equipped with the supporting mechanism.
For improving recording density of the magnetic disk device, reduction of the magnetic spacing., that is, the distance between a top of a magnetic gap of the magnetic head and a surface of the recording layer of the magnetic disk has been pursued earnestly together with improvement of magnetic characteristics of the magnetic head and the magnetic disk.
As to a read/write system having a conventional flying type magnetic head wherein the magnetic spacing is defined by thickness of a protection film for protecting the slider surface facing the air bearing, thickness of a protection film and/or a lubrication film of the magnetic disk surface, roughness of the magnetic disk surface, and so on, the magnetic spacing of about 40 to 50 nm is attained now.
However, the magnetic spacing is considered to be less than 15 nm for realizing recording density of 10 to 20 G bits/inch.sup.2 or more.
For enabling such small magnetic spacing, contact-type magnetic disk devices, which have a magnetic head operating in continuous sliding contact with recording media, have been developed, wherein magnetic information is recorded and reproduced by a magnetic head mounted on a head slider sliding on a surface of a magnetic disk continuously contacting with the disk surface. An example thereof is introduced in "Contact Recording on Perpendicular Rigid Media" by H. Hamilton, the Journal of Magnetic Society of Japan, vol. 15, Supplement No. S2 (1991), pp. 483-490.
FIG. 8 is a schematic diagram illustrating a basic configuration of the contact-type magnetic disk device.
The contact-type magnetic disk device of FIG. 8 comprises a contact-type magnetic head 107 for reading/writing information on a magnetic disk D, a head slider 101 whereon the contact-type magnetic head 107 is mounted, and a beam suspension 106 for supporting the head slider 101 having contact pads 108 and 109 to be pushed onto the magnetic disk D.
The beam suspension 106 is fixed to a positioning actuator 102, which takes charge of positioning the contact-type magnetic head 107 on a desired track of the magnetic disk D, by way of a positioning actuator arm 112. The beam suspension 106 is made of a leaf spring and pushes the head slider 101 onto the magnetic disk D with its flexural rigidity.
FIGS. 9A to 9C are perspective views illustrating details of the head slider 101 and the beam suspension 106 of FIG. 8. As shown in FIG. 9A, the head slider 101 is set at a top part of the beam suspension 106 whereon electric wirings 113 are printed directly. FIG. 9B illustrates an enlargement of the head slider 101 wherein the magnetic head 107 is configured, and FIG. 9C illustrates an enlargement of a half cut of the contact pad 108, which is provided on an under-surface of the head slider 101 so that the magnetic head 107 can perform contact reading or writing by way of a yoke 111 penetrating through the contact pad 108.
In the above basic example, the beam suspension 106 is made of a simple leaf spring. However, in many cases, a secondary suspension such as a gimbal is further provided for improving follow-up performance of the head slider to the disk surface. An example thereof is illustrated in FIG. 10, wherein the same or the corresponding parts with the magnetic disk device of FIG. 8 are denoted by the same numerals and the duplicated descriptions are omitted.
In the conventional example of FIG. 10, the head slider 101 is supported by a gimbal 121 which is fixed to the beam suspenision 106, and the head slider 101 is pushed to the magnetic disk D by the beam suspension 106 through the gimbal 121.
In a still another example disclosed in a Japanese patent application laid open as a Provisional Publication No. 250793/'93, the magnetic head is supported by the head slider by way of minute springs which act as secondary springs for improving the follow-up performance of the magnetic head in a high frequency range.
The supporting mechanism of the head slider is required to have sufficiently high rigidity in a radial direction of recording tracks of the magnetic disk (rotating direction of the beam suspension), for realizing sufficiently high-speed and precise seeking movement on the disk surface, and to have sufficiently strength in a tangential direction of the recording tracks, against frictional and viscous resistance of lubricant applied between the head slider and the disk surface.
On the other hand, the supporting mechanism is required as well to have certain flexibility or compliance for allowing rolling (rotating around an axis in the tangential direction of the recording tracks) and pitching (rotating around an axis in the radial direction of the recording tracks) movement of the head slider so that the head slider can follow the disk surface adequately. The flexibility of the supporting mechanism pertains also deeply to setting margins for assembling the magnetic disk device. The larger the flexibility is, the larger setting margins are obtained.
Furthermore, the load of the suspension to push the contact slider towards the disk surface should be considerably small in the contact-type magnetic disk device, compared to ordinary flying-type magnetic head system, for reducing frictional and viscous resistance and wearing of the head slider.
However, the small load and the high rigidity of the suspension in the pitching and the rolling direction of the head slider makes unstable the posture of the head slider, and the continuous sliding contact between the pad surface and the disk surface can not be maintained when there is provided but one contact pad, or, even when more than one contact pads are provided, the unstable posture produces unequal pad pressures and jumping of a specific pad, resulting in degradation of recording/reproducing characteristics of the magnetic head.
Therefore, the rigidity of the suspension in the pitching and the rolling direction of the head slider should be also designed to be small in proportion to the pushing load.
As above described, two conflicting requirements, rigidity and flexibility are imposed onto the supporting mechanism of the contact-type head slider.
When priority is given to the flexibility, sufficient rigidity of the suspenision in its rotating direction for suppressing at vibration mode of the suspension in the accessing direction cannot be obtained and rigidity against a primary or a secondary vibration mode of the suspension system becomes low, resulting in increase of vibration amplitude as well as at fall of resonance frequency of each vibration mode.
The vibration of the head slider or the suspension system, whereof frequency ranges are out of controllable frequency band, produces off-track of the magnetic head from the data tracks recorded on the magnetic disk. Therefore, the recording/reproducing operation of the magnetic head is forced to wait for attenuation of these vibration modes which are excited by every accessing movement. Furthermore, even in the track following movement, the off-track may be caused by vibration being stimulated by external noises other than the accessing movement.
These problems have been an obstacle to the high-speed and the high-density recording/reproduction.
On the other hand, when the gimbal rigidity is made comparatively high to the contacting rigidity between the head slider and the magnetic disk, (namely, the film tension when there is provided a lubrication film, or the pushing, force of the suspension when there is no lubrication film,) assembling tolerances become severe and pressure of each contact pad becomes easy to vary. Therefore, the contact sliding between the head slider and the disk surface becomes unstable because of degradation of the the follow-up performance of the head slider to the disk surface, which not only accelerates wearing of the head slider and the magnetic disk, but also makes high the error rate through fluctuation of signal intensity caused by jumping of the head slider, resulting in poor HDI (Head-Disk Interface) reliability.
These are the problems included in the conventional supporting mechanism of the magnetic head slider.